SFTSV utilizes AXL/GAS6 for entry via PI3K-PLC-dependent macropinocytosis activated by AXL-kinase

Severe fever with thrombocytopenia syndrome (SFTS) is a significant public health concern caused by SFTS virus (SFTSV), a tick-borne RNA virus. Previous studies have identified DC-SIGN and related C-type lectins as receptors of SFTSV infection in specific cell populations. Our genome-wide CRISPR activation screening identified AXL, a receptor tyrosine kinase, as a novel entry receptor for SFTSV. We found that AXL-mediated SFTSV infection utilizes the bridging action of growth arrest-specific protein 6 between AXL and phosphatidylserine on virus particles. This interaction induces autophosphorylation of tyrosine residues in the intracellular domain of AXL, recruiting phosphatidylinositol-3 kinase (PI3K) and phospholipase C (PLC) and establishing a macropinocytotic pathway of SFTSV entry. The AXL-PI3K-PLC-dependent entry pathway was observed in diverse cell types, including human umbilical vein endothelial cells (HUVEC), offering deep insights into the lifecycle of SFTSV and offering AXL as a novel therapeutic target against SFTS.IMPORTANCEUnderstanding the molecular mechanisms of viral entry is critical for developing targeted antiviral therapies since there is no effective vaccine or antiviral drug against severe fever with thrombocytopenia syndrome (SFTS). This study uncovered AXL as a potential entry receptor for SFTS virus (SFTSV) via PI3K/PLC-dependent macropinocytosis pathway distinct from previously reported viral entry mechanism. The inhibition of these cellular enzymes resulted in the suppression of SFTSV infection in the AXL-expressing cell lines and HUVEC. Our research sheds light on the intricate molecular mechanisms underlying these interactions by utilizing mutants of AXL and represents a promising target for the development of innovative therapeutics against SFTS.